To increase production of a well, it is often necessary to fracture the well, which is performed by flowing fracturing fluid into the earth to mechanically create cracks in the ground. Fracturing fluid typically includes a liquid mixed with sand, small ceramic beads, or similar proppant material, which creates pressure within the well as the fluid accumulates, until the pressure causes cracks to form in the earth, or causes existing cracks in the earth to widen, thereby increasing the flow of hydrocarbons from the well.
Conventionally, when fracturing a well, numerous manifolds, i.e. a pumping manifold, a flowback manifold, a choke manifold, and other manifolds, must be installed at the wellhead surface, which can require six to eight hours, or longer, numerous personnel, and a large amount of space on a rig floor. Additionally, each manifold requires a series of hydraulic conduits or similar connections to enable actuation of the manifold, which further consumes limited space proximate to a wellhead and can create a safety hazard.
Fractionation manifolds typically include a series of valves and connectors used to flow fracturing fluid from a fluid vessel into the wellhead. Fluid is then retrieved from the wellhead and is flowed through different valves into a choke, which controls the back pressure on the well and ensures the flow of fluid directly through the choke. Sand, beads, and other particulates in the fluid are sent through a reverse line overboard, or to a pickle return tank, while the fluid, itself, can be reclaimed through a separate reverse line to the rig pits for treatment. Operation of the valves and chokes normally requires at least one operator, on-site, to manipulate appropriate hydraulic, electrical, and/or manual parts of the manifolds. Often, the one or more operators can be subject to inclement weather, and potential safety risks when manipulating the manifolds.
To reduce the possibility of choke failure, many fractionation manifolds incorporate use of an auxiliary choke. The primary and auxiliary chokes both communicate with the tubing string of the well, so that the auxiliary choke can be engaged if the primary choke fails.
A typical fractionation system, especially a system incorporating a second choke, is extremely large, cumbersome, and expensive, containing a large number of valves and connectors, and requiring a large number of hoses and conduits to ensure sufficient electrical and/or hydraulic connections. Additionally, most fractionation manifolds are difficult and time consuming to properly install, each valve and component requiring precise alignment using cranes and other devices adapted for manipulation of the heavy components. Further, most fractionation manifolds are limited regarding the orientation with which components can be installed and engaged, which can become a hindrance on offshore rigs and other drilling sites where space is limited. Also, most fractionation manifolds require on-site personnel to actuate valves, chokes, and other parts of the manifolds, increasing the time required for each operation, and the inherent risk to the operators.
Also, a typical fractionation system is limited to a flow rate of approximately 30 barrels of fluid per minute. When additional flow is necessary, multiple manifolds are used, increasing the time, expense, and space required, and necessitating additional cumbersome installation and operating procedures necessary to fracture and produce a well.
A need exists for a fractionation system that can be used to perform the functions of numerous manifolds using a single, readily transportable system that is efficient to install, remotely operable, and able to exceed the flow capacity of conventional manifolds while eliminating the need for numerous hydraulic and electrical lines, and the need for operators to be present on the rig floor during the fractionation process, thereby providing a significant safety benefit.
A need also exists for a fractionation system that can advantageously utilize limited space at a drilling site by enabling selective engagements of differing orientation between fractionation manifolds and chokes.
A further need exists for a fractionation system that can incorporate a second choke that is in communication with the casing of a drill string, rather than the tubing string, that is useable both as a backup choke during primary choke failure, and that is separately useable during sandouts to remove excess return fluid from a well.
An additional need exists for a fractionation system that is modular, able to be efficiently and easily aligned and installed through use of interlocking skids, or alternatively, a single unitary skid or similar transport member, that is able to accommodate flow rates in excess of conventional manifolds using only a single fractionation manifold and a single power unit.
Embodiments of the present invention meet these needs.